This study will define the mechanism by which pemphigus antibody induces acantholysis. Pemphigus antibody has been incubated with human epithelial cells to activate or secrete a proteinase which produces cell dyshesion. Viable epithelial cells are necessary for this event to occur. A proteinase has been purified from mouse and human epithelial cells which when incubated with epidermal cells causes dyshesion. Studies are being performed to determine if this is the enzyme which produces acantholysis in viable epidermal cells.